Exhaust apparatus of vehicles

ABSTRACT

A first muffler (4) is connected to a rear end portion of the exhaust pipe (2) extending from a single-cylinder engine toward one side of a rear portion of the vehicle body and is provided on one side of the vehicle body. A second muffler (5) is provided on the other side of the vehicle body opposite to the first muffler (4) through a connecting pipe (6). An outer side surface near the front end portion of the first muffler (4) and the second muffler (5) are covered with first and second covers (7) and (8) both plated. Each of the exhaust pipe (2) and the first and second mufflers (4) and (5) have double-pipe structure with outside plated. Further, a front end portion of the second cover (8) is curved toward the center of the vehicle body, and a phantom line as a continuous frontward extension from the front end portion of the second cover (8) is positioned before the axis of the connecting pipe (6).

This application is the national phase under 35 U.S.C. §371 of prior PCTInternational Application No. PCT/JP97/03975 which has an Internationalfiling date of Oct. 31, 1997 which designated the United States ofAmerica.

FIELD OF THE INVENTION

The present invention relates to an exhaust device having a pair ofmufflers on the right and left sides of a vehicle body in a vehicle suchas a motorcycle on which a single-cylinder engine is mounted.

DESCRIPTION OF THE PRIOR ART

Japanese Patent Laid-open No. 2-241920 discloses an exhaust devicehaving a pair of mufflers on the right and left sides of a vehicle bodyin a motorcycle on which a single-cylinder engine is mounted.

This exhaust device includes an exhaust pipe extending from thesingle-cylinder engine toward one side of a rear portion of the vehiclebody, a first muffler connected to a rear end portion of the exhaustpipe and provided on one sides of the vehicle body, a second mufflerprovided on the other side of the vehicle body opposite to the firstmuffler, and a connecting pipe for connecting a front end portion of thesecond muffler and a front end portion of the first muffler so as toextend laterally of the vehicle body.

While the surface of an outward appearing portion of the exhaust deviceis required to be plated, such a plated portion is possibly discoloredby exhaust heat. To prevent such discoloration, each of the exhaustpipe, the connecting pipe, and the first and second mufflers must beformed to have a double-pipe structure, and the outer surface of eachcomponent must be plated.

However, the connection between these double-pipe structural componentsis complicated in structure, and much time is required formanufacturing. Further, if the connecting portion is formed to have asingle-pipe structure, the plated surface of the exhaust device as awhole becomes discontinuous, and partial discoloration occurs, so thatit is difficult to maintain the appearance of the exhaust pipe good.

It is accordingly an object of the present invention to provide anexhaust device for use with a single-cylinder engine in which a pair ofmufflers can be provided on the opposite sides of a vehicle body withoutdamage to the appearance, and a good look can be maintained with easymanufacturing.

DISCLOSURE OF THE INVENTION

FIG. 1 shows the principle of the present invention. As shown in FIG. 1,the exhaust device for vehicle according to the present inventionincludes a single-cylinder engine 1, an exhaust pipe 2 extending fromthe single-cylinder engine 1 toward one side of a rear portion of avehicle body, a branch and joint member 3 connected to a rear endportion of the exhaust pipe 2, a first muffler 4 connected to a rear endportion of the branch and joint member 3 and provided on one side of thevehicle body, a second muffler 5 provided on the other side of thevehicle body opposite to the first muffler 4, a connecting pipe 6connecting a front end portion of the second muffler 5 and the branchand joint member 3 and extending laterally of the vehicle body, a firstcover 7 for covering an outer side surface of the branch and jointmembers 3, and a second cover 8 for covering an outer side surface of aconnecting portion between a front portion of the second muffler 5 andthe connecting pipe 6.

Each of the exhaust pipe 2, the first muffler 4, and the second muffler5 has a double-pipe structure with outside plating. Each of the branchand joint member 3 and the connecting pipe 6 has a single-pipestructure. Each of the first and second covers 7 and 8 is plated.

Preferably, a front end portion of the second cover 8 is curved towardthe center of the vehicle body, and a phantom line as a continuousfrontward extension from the front end portion of the second cover 8 ispositioned before the axis of the connecting pipe.

The rear end portion of the exhaust pipe 2 having a double-pipestructure and the front end portion of the first and second mufflers 4and 5 both having a double-pipe structure are connected together throughthe branch and joint member 3 and the connecting pipe 6 both having asingle-pipe structure. Accordingly, the connection structure of eachconnecting component can be simplified and the exhaust device can beeasily manufactured.

Further, the outer side surface of these single-pipe structuralcomponents 3 and 6 that are prone to discoloration due to exhaust heatare covered with the first and second covers 7 and 8 both plated, thatis, concealed from side view. Further, the first and second covers 7 and8 are continuous in appearance to the mufflers. Accordingly, the firstand second covers 7 and 8 readily look like continuous portions ofexhaust device rather than mere separate covers that may look as if theyare raised from their surrounding parts. Thus, the appearance of theexhaust device as a whole can be made into a condition such that it issubstantially uniformly plated without any discoloration due to exhaustheat.

Although the single-cylinder engine 1 is mounted on the vehicle, thepair of mufflers 4 and 5 can be provided on the opposite sides of thevehicle body without damage to the appearance, and it is possible toobtain an exhaust device having a good look as a whole and easy tomanufacture.

Further, in the case that the front end portion of the second cover 8 iscurved toward the center of the vehicle body, and the phantom linecontinuously extending frontward from the front end portion of thesecond cover 8 is positioned before the axis of the connecting pipe 6,the second muffler 5 looks as if it is directly connected through thesecond cover 8 to a virtual exhaust pipe 9 shown in FIG. 1. Furthermore,the presence itself of the second cover 8 is not so visually felt,thereby providing natural feeling to the exhaust device as a whole andfurther improving the appearance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view illustrating the principle of the presentinvention;

FIG. 2 is a left side view showing the appearance of a vehicle body of amotorcycle to which the present invention is applied;

FIG. 3 is a right side view of the motorcycle;

FIG. 4 is a top plan view of the motorcycle;

FIG. 5 is a bottom plan view of the motorcycle;

FIG. 6 is a left side view of a left-hand part of an exhaust device witha first cover being separated;

FIG. 7 is a top plan view of the left-hand part;

FIG. 8 is a horizontal sectional view of the left-hand part with anexhaust pipe being not shown;

FIG. 9 is an enlarged cross section taken along the line 9--9 in FIG. 7;

FIG. 10 is a horizontal sectional view of a right-hand part of theexhaust device;

FIG. 11 is a vertical sectional view of the righthand part;

FIG. 12 is a side view of a second cover;

FIG. 13 is a top plan view of the second cover; and

FIG. 14 is an enlarged cross section taken along the line 14--14 in FIG.13.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 2 to 5, an embodiment according to the presentinvention is explained. Hereafter, the same reference numeral is usedfor such a common functional part as shown in FIG. 1. The motorcycleincludes a single-cylinder engine 1 supported by a body frame 12 betweena front wheel 10 and a rear wheel 11. An exhaust pipe 2 connected at oneend thereof to the engine 1 extends rearward along the lower side of theengine 1 toward the left side of the vehicle body. The other end of theexhaust pipe 2 is connected through a branch and joint member 3 to afirst muffler 4 extending along the left side of the rear wheel 11.

A second muffler 5 is provided on the right side of the vehicle body soas to extend along the right side of the rear wheel 11. A front endportion of the second muffler 5 is connected to the branch and jointmember 3 by means of a connecting pipe 6 extending laterally of thevehicle body. An outer side surface of the branch and joint member 3 iscovered with a first cover 7 so as to be externally invisible from theleft side of the vehicle body. Similarly, an outer side surface of aconnecting portion between a front portion of the second muffler 5 andthe connecting pipe 6 is covered with a second cover 8 so as to beexternally invisible from the right side of the vehicle body.

A front fork 13 supporting the front wheel 10 is pivotably supported toa head pipe 14, and is steered by handlebars 15. Reference numeral 16denotes a handgrip, and reference numeral 17 denotes a steering lock.

The front wheel 10 includes a spoke wheel 18 formed of a light alloy orthe like. A brake disc 19 is provided on one side of the spoke wheel 18,and is braked by a brake caliper 20. Reference numeral 21 denotes afront fender.

An upper portion of a cylinder portion 22 of the engine 1 is coveredwith a front side cover 23. A carburetor 24 is provided behind thecylinder portion 22. A self-starting motor 26 is provided at an upperportion of a crankcase 25 located beneath the cylinder portion 22.

A gearshift pedal 27 is provided at a lower front portion of thecrankcase 25 on the left side of the vehicle body, and a brake pedal 28is provided at the same portion on the right side of the vehicle body.

The body frame 12 is of a cradle type including a main frame 12aextending longitudinally of the vehicle body at an upper positionthereof, a pair of right and left front down frames 12b extendingdownward and rearward from the head pipe 14, a pair of right and leftlower frames 12c extending substantially horizontally rearward from thelower ends of the right and left front down frames 12b and supporting alower portion of the crankcase 25, a pair of right and left rear stays12d extending upward and rearward from the rear ends of the right andleft lower frames 12c, and a pair of right and left center down frames12e extending downward and rearward from the rear end of the main frame12a.

A pair of right and left footrests 29 for a rider are mounted on theright and left lower frames 12c at their respective front portions. Aside stand 30 is pivotably supported to the left lower frame 12c at aposition behind the left footrest 29.

A pair of right and left pivot plates 31 are supported to the right andleft rear stays 12d and the right and left center down frames 12c attheir respective lower end portions. Each pivot plate 31 is providedwith a pivot portion 32 for pivotably supporting a front end portion ofa rear swing arm 33. A pair of right and left footrests 34 for apassenger are mounted on the right and left rear stays 12d.

A fuel tank 35 is supported on the main frame 12a above the cylinderportion 22. A rider's seat 36 and a passenger's seat 37 are provided intandem behind the fuel tank 35. The passenger's seat 37 is supported ona rear fender body portion 38.

A rear fender tail portion 39 extends downward and rearward from therear end of the rear fender body portion 38. A pair of right and leftgrab rails 40 are provided on the right and left side surfaces of therear fender body portion 38 so as to extend rearward from the driver'sseat 36.

A vertically extending backrest stay 41 is supported at its right andleft lower ends to the rear portions of the right and left grab rails40. A backrest 42 is supported to the backrest stay 41 at its upperportion.

In FIGS. 2 and 3, reference numeral 43 denotes a top bridge, 44 a bottombridge, 45 a side cover, and 46 a substantially disk-shaped dish wheel.

As apparent from FIG. 5, a cross pipe 47 is provided between the rightand left lower frames 12c in the vicinity of a bottom rear position ofthe crankcase 25. A pivot portion 29 of a main stand 48 is pivotablysupported to the cross pipe 47.

The pivot portion 49 is located before the connecting pipe 6, and themain stand 48 in its retracted condition is located below the connectingpipe 6. Accordingly, the connecting pipe 6 is covered on its front andlower side with the main stand 48 during running of the vehicle, therebybeing protected against a bouncing stone coming from the front wheel 10.

Electrical components mounted on the motorcycle include a headlight 50,front turn signals 51, horn 52, rear turn signals 53, and taillight 54.

As apparent from FIG. 4, various indicators 55 are provided on the topbridge 43. A projecting portion 56 is formed on the upper surface of thefuel tank 35, and a meter 58 is provided on the projecting portion 56 ata position before a fuel filler opening 57.

The structure of the exhaust device will now be described in detail withreference to FIGS. 6 to 14. Although not shown, the exhaust pipe 2 has adouble-pipe structure and is generally plated. A nut portion 60 isprovided on the outer side surface of the exhaust pipe 2 at its rear endportion.

As apparent from FIG. 8, the branch and joint member 3 has a single-pipestructure, and it is integrated with the front end of the first muffler4 by welding. A bracket 61 is mounted on the outer side surface of thebranch and joint member 3. The bracket 61 is formed with two hooks 62raised from the outer side surface of the branch and joint member 3.

The inner side surface of the branch and joint member 3 is formed with aside connection opening 63, and a left connecting pipe member 6a isconnected with the side connection opening 63. The left connecting pipemember 6a has a connection end portion 64 adapted to engage a joint 65(see FIG. 10) of a right connecting pipe member 6b.

That is, the connecting pipe 6 can be divided at its intermediateportion into the right and left connecting pipe members 6a and 6b, andhas a single-pipe structure as a whole.

The first muffler 4 has a double-pipe structure composed of an outerwall 66 and an inner wall 67, and the internal structure of the firstmuffler 4 is similar to that of a known muffler such that the insidespace is separated into a plurality of chambers. The outer surface ofthe outer wall 66 is generally plated.

As apparent from FIGS. 6 and 7, the first cover 7 is formed from asuitable material such as an iron plate. The first cover 7 has asubstantially triangular shape as viewed in side elevation so as to befitted with the outer side surface of the branch and joint member 3.Further, as apparent from FIG. 9, the cross section of the first cover 7along a direction perpendicular to the longitudinal direction of thefirst cover 7 is substantially semicircular. The outer surface of thefirst cover 7 is also generally plated.

A through hole 68 is formed at a front end portion of the first cover 7.As apparent from FIG. 9, two stays 69 are mounted on the inner surfaceof the first cover 7 at its rear portion, so as to form two tunnel-likeholes 69a for respectively engaging the two hooks 62.

As apparent from FIG. 10, the right connecting pipe member 6b is bent atits rear end portion to extend rearward, and is connected to a front endportion of the second muffler 5. The second muffler 5 is similar instructure to the first muffler 4, that is, the second muffler 5 has adouble-pipe structure composed of an outer wall 70 and an inner wall 71,and the inside space of the second muffler 5 is separated into aplurality of chambers. The outer surface of the outer wall 70 isgenerally plated.

Only the front end portion of the second muffler 5 is formed as a frontcap 72 having a single-pipe structure. The front cap 72 is engaged withand welded to the front end of a body portion of the second muffler 5having a double-pipe structure. The rear end portion of the rightconnecting pipe member 6b is connected to the front cap 72. A bracket 73having two hooks 74 is welded to the outer surface of the front cap 72.The hooks 74 are raised from the outer surface of the front cap 72 andextend frontward.

As apparent from FIGS. 12 to 14, the second cover 8 has a structuresubstantially similar to that of the first cover 7, and the outersurface of the second cover 8 is also generally plated.

As apparent from FIG. 13, the second cover 8 is curved in such a mannerthat it forms a curved line extending from the front cap 72substantially along a bent portion 75 of the right connecting pipemember 6b, and a front end portion 76 of the second cover 8 is directedtoward the center of the vehicle body. That is, a phantom line A showinga continuous frontward extension from the front end portion 76 of thesecond cover 8 is directed toward the engine 1 located at the laterallycentral position of the vehicle body (see also FIG. 1).

As apparent from FIG. 10, the phantom line A forms an angle θ withrespect t o the axis B of the right connecting pipe member 6b. Thefarther the phantom line A extends frontward from the front end portion76 of the second cover 8, the larger the distance between the phantomline A and the axis B becomes. The axis B of the right connecting pipemember 6b is identical with the axis of the connecting pipe 6.

A through hole 77 is formed at a front portion of the second cover 8. Asshown in FIG. 14, two stays 78 are mounted on the inner surface of thesecond cover 8 at its rear portion, so as to form two tunnel-like holes79 for respectively engaging the two hooks 74.

The structure of the first and second mufflers 4 and 5 will now bedescribed in brief. The first muffler 4 is connected at its open frontend of the branch and joint member 3, and the inside space of the firstmuffler 4 is separated into first, second, and third extension chambers84, 85, and 86 by means of first and second separators 81 and a tail cap83.

The first expansion chamber 84 and the third expansion chamber 86communicate with each other through a first communication pipe 87. Thethird expansion chamber 86 and the second expansion chamber 85communicate with each other through a second communication pipe 88. Thesecond expansion chamber 85 and the atmosphere communicate with eachother through a third communication pipe 89.

The branch and joint member 3 is provided with a separator 80 locatedbehind the side connection openings 63. As apparent from an enlargedview in FIG. 8, the separator 80 has a central hole 80a for passing theexhaust pipe 2 and a plurality of openings 80b formed around the centralhole 80a. A part of exhaust gas discharged from the exhaust pipe 2 intothe first expansion chamber 84 is allowed to pass through the openings80b of the separator 80 and flow through the side connection openings 63toward the second muffler S as shown by an arrow P in FIG. 8.

Similarly, the inside space of the second muffler 5 is separated intofirst, second, and third expansion chamber 94, 95, and 96 by means offirst and second separators 91 and 92 and a tail cap 93.

The first expansion chamber 94 and the third expansion chamber 96communicate with each other through a first communication pipe 97. Thethird expansion chamber 96 and the second chamber 95 communicate witheach other through a second communication pipe 98. The second expansionchamber 95 and the atmosphere communicate with each other through athird communication pipe 99.

The operation of this preferred embodiment will now be described. Inmounting the first cover 7, it is first placed on the outer side surfaceof the branch and joint member 3 and next moved rearward to makeengagement of the hooks 62 with the holes 69a of the stays 69 mounted onthe inner surface of the first cover 7 as shown in FIGS. 6 and 7.

Thereafter, the hole 68 formed at the front end portion of the firstcover 7 is aligned with the nut portion 60 formed at the rear portion ofthe exhaust pipe 2, and a bolt (not shown) is engaged with the nutportion 60 through the hole 68, thereby securing the first cover 7 tothe exhaust pipe 2 and the branch and joint member 3. Thus, the firstcover 7 is mounted on the branch and joint member 3 so as to cover theouter side surface of the branch and joint member 3, thereby concealingit from side view. Furthermore, the first cover 7 looks as if itcontinues to the rear end portion of the exhaust pipe 2 and the frontend portion of the first muffler 4.

In mounting the second cover 8, it is first placed on the outer sidesurface of the bent portion 75 of the right connecting pipe member 6band next moved rearward to make engagement of the hooks 74 with theholes 79 of the stays 78 as shown in FIGS. 10 to 14. The hole 77 formedat the front end portion of the second cover 8 is aligned with a nutportion 75a (see FIG. 10) formed at the bent portion 75, and a bolt (notshown) is engaged with the nut portion 75a through the hole 77, therebysecuring the second cover 8 to the right connecting pipe member 6b andthe front cap 72.

Accordingly, the second cover 8 is so mounted as to cover the outer sidesurface of at least the bent portion 75 of the right connecting pipemember 6b and the front cap 72. Thus, a portion of these single-pipestructural components appearing outward of the vehicle body is concealedfrom side view.

As a result, all the externally visible portions of the exhaust deviceon the right and left sides of the vehicle body look as if they aresubstantially uniformly plated. Accordingly, even if the single-pipestructural components (3, 6, 72) are discolored by exhaust heat, theappearance of the vehicle body is not damaged.

Furthermore, the first cover 7 plated looks as if it continues to theexhaust pipe 2 and the first muffler 4 both plated, and the second cover8 plated similarly looks as if it continues to the second muffler 5plated. Accordingly, the first and second covers 7 and 8 readily looklike continuous portions of the exhaust device rather than mere separatecovers that may look as if they are raised from their surrounding parts.Thus, the appearance of the exhaust device as a whole can be made into acondition such that it is substantially uniformly plated without anydiscoloration due to exhaust heat.

Accordingly, all of the branch and joint member 3, the connecting pipe6, and the front cap 72 concealed by the first and second covers 7 and 8can be formed as a singlepipe structural components without plating. Byconnecting the rear end portion of the exhaust pipe 2, the first muffler4, and the second muffler 5 each having a double-pipe structure throughthe above single-pipe structural components, the connection structure ofeach connecting component can be simplified and the exhaust device canbe easily manufactured.

Although the single-cylinder engine 1 is mounted on the motorcycle, thepair of mufflers 4 and 5 can be provided on the opposite sides of thevehicle body without damage to the appearance, and it is possible toprovide an exhaust device having a good look as a whole and easy tomanufacture.

Further, the front end portion of the second cover 8 is so curved as tobe directed toward the engine 1 located at the laterally centralposition of the vehicle body, and the phantom line A continuouslyextending frontward from the front end portion of the second cover 8 ispositioned before the axis B of the connecting pipe 6 (see FIGS. 10 and13) . Accordingly, the second muffler 5 looks as if it is directlyconnected to a virtual exhaust pipe 9 (see FIG. 1) which is connected tothe engine 1.

Further, the second cover 8 readily looks as if it is a part of thesecond muffler 5 and the presence itself of the second cover 8 is notvisually felt, thereby providing natural feeling to the exhaust deviceas a whole and further improving the appearance.

INDUSTRIAL APPLICABILITY

As described above, the exhaust device for vehicles according to thepresent invention is available to the exhaust system of the motorcycleincluding an exhaust pipe extending from the engine toward the centerportion or one side of the vehicle body and the mufflers provided on theright and left side of the vehicle body connecting to the rear endportion of the exhaust pipe. It is especially favorable for the singlecylinder type engine, and is further applicable also for the varioustypes of the engine having tandem cylinders, V-type plural cylinders andthe like.

What is claimed is:
 1. In an exhaust device for a vehicle including asingle-cylinder engine, an exhaust pipe (2) extending from saidsingle-cylinder engine toward one side of a rear portion of a vehiclebody, a first muffler (4) connected to a rear end portion of saidexhaust pipe (2) and provided on one side of said vehicle body, a secondmuffler (5) provided on the other side of said vehicle body opposite tosaid first muffler (4), and a connecting pipe for connecting said secondmuffler and said exhaust pipe, said connecting pipe (6) extendinglaterally of said vehicle body, each of said exhaust pipe (2), saidfirst muffler (4), and said second muffler (5) having a double-pipestructure with outside plating; the improvement wherein:said rear endportion of said exhaust pipe is connected through a branch and jointmember (3) having a single-pipe structure to a front end portion of saidfirst muffler (4); an end portion of said connecting pipe (6) having asingle-pipe structure is connected to said branch and joint member (3);an outer side surface of said branch and joint member (6) is coveredwith a first cover (7) plated; and an outer side surface of a connectingportion (3) between a front portion of said second muffler (5) and saidconnecting pipe (6) is covered with a second cover (8) plated.
 2. Anexhaust device for a vehicle according to claim 1, wherein a front endportion of said second cover (8) is curved toward the center of saidvehicle body, and a phantom line continuously extending frontvard fromsaid front end portion of said second cover (8) is positioned before theaxis of said connecting pipe (6).